Both in human therapy and in veterinary medicine it is frequently required to provide support for a body portion of the subject or patient, either for immobilizing parts of the supported portion, immobilizing the supported portion relative to other parts of the body or to provide load-bearing members adapted to take up forces which should not be applied to the supported body portion.
Typical of such supporting devices are braces and splints. However, for the present purposes it should be noted that the term "body support" or "splint" may be used interchangeably to refer to any device which can be shaped to the contours of a human or animal body or a portion thereof to stabilize such portion, to provide a load-supporting structure and encase the same fully or partially, or a structure cushioning the portions of the body against impact or other detrimental environmental effects.
Thus the terms will include braces, splints, stiffening members and cushioning structures to support broken limbs, to provide therapeutic regulation of the stance of the body, to impart a desired position to a supported portion or to immobilize the supported portion relative to other parts of the body.
Various devices for the latter purposes have been proposed heretofore and one can generally recognize such qualities in plaster casts, splints and braces of wood, synthetic resin, plastic or metal.
Generally the conventional devices are designed to limit the movement of a part of the body, e.g., the arm, leg, foot or neck, to allow healing of muscular disorders, joint disorders or fractures, to provide structural support for the body portions so that the patient or subject can have improved mobility or to prevent movement of body portions where such movement would be detrimental to healing of burns or the like. For example, there are disorders such as irritations in which absolute or partial immobility of a body member is required for healing.
The procedure in the past has been to place the body portion or member in the desired position at which healing will be optimum and to apply a plaster strip (after wetting) so that, upon hardening of the resulting cast, a change from this position will be resisted.
While the body portion or member is held generally in a desired position, there nevertheless is the requirement that some mobility be provided. Such mobility is necessary to prevent atrophying, or blood-circulation disorders, or to prevent deterioration of the skin resulting from lack of activity. Furthermore, total immobility may affect other portions of the body and may even adversely affect the functioning of the immobilized part or member if the immobilization is to extend over prolonged periods.
Disorders which must be treated by casts, splints, braces and other immobilizing (generally: supporting) devices occur daily in sports, hazardous occupations and even day-to-day life, with humans as well as with animals.
It has been found that similar problems arise in orthopedics with disorders of the bone structure and musculature systems, e.g., curvature of the legs, foot disorders, disorders of the spinal column and deterioration of the joints as a result of congenital defects, diseases and age. In these cases as well it is necessary to immobilize or support portions of the body and supporting devices in the form of corsets, cases and prostheses or the like are required and may be formed from plaster or, expecially in the form of prostheses-carrying cases from stiff but cushioning synthetic materials. In all circumstances, however, these devices must be conformed to the body.
In general there are three methods used in the art for providing supporting devices for the purposes described.
Probably the best known and most widely used technique is the application of a plaster cast using plaster-containing bands or strips which are immersed in water and wound upon the body portions to be supported. By hand-shaping the plaster mass can be so molded that the cast can conform to the body portions and also assume substantially any position in which it may be desirable to support the body. By chemical reaction or evaporation of water the support hardens and maintains its preset position and shape.
Another type of support is provided by use of air-impermeable bags which are filled with a granular material and are laid upon the portion of the body to be supported. These bags are evacuated by a pump so that atmospheric pressure applies to the bag a force which presses against the filling and makes the bag relatively stiff and immovable. It is also known to connect the interior of such bags with an air source so that the bag can be firmly mounted upon the body portion to be supported.
A third type of supporting device utilizes a synthetic-resin in liquid or plastic form, with or without reinforcing inlays of a textile fabric, which are applied to the body portion to be supported and are hardened by heat or ultraviolet radiation.
The disadvantages of the different techniques are set forth in the following Table:
__________________________________________________________________________ Plaster of Paris/ Vacuum bag Synthetic-Resin Starch-Bandage Bandage __________________________________________________________________________ Time Long time needed for Short time for Medium time for hardening, a number achieving hard- hardening, of hours up to days. ness, not form- little formability. able due to lack of plasticity. __________________________________________________________________________ Weight High because of density Medium high, depend- Low because of of material, the neces- ent on filling mat- small density and sary volume and inserts. erial in bags, but little needed constant pressure on volume, the part of the body and danger of circu- latory disorders, so that model is only a temporary arrange- ment, e.g. for trans- port purposes, but unusable for thera- peutic treatment. __________________________________________________________________________ Porosity Little receptivity Nonporous for air Little porosity for steam, i.e. water, and water, i.e. because of supports Plaster of Paris is steam. Short usable for air and water. hygroscopic. Through service life. Little Good water intake diminishes for transparency considerably. Disrup- transparency for X-rays. tive absorption when X-rays. illuminated by X-Ray. __________________________________________________________________________ Sensitivity Not waterproof. Unbreak- Sensitive to mech- Generally water- able only after increased anical damage of bag, proof and mech- strength; i.e. weight. limitedly stable. anically stable. __________________________________________________________________________ Equipment Little, manual skill Considerable, since Medium, since mix- is necessary special bag forms ing apparatus and are needed for each gear are necessary part of the body and for introducing a vacuum pump hardness __________________________________________________________________________
From the Table it will be apparent that none of the conventional techniques is fully satisfactory. In the past the short period required to apply the support has given a slight advantage to the plaster cast or strip, although such supports have disadvantages when the body portion must be subjected to X-ray. Recently synthetic-resin supports have become a more interesting alternative because of X-ray transparency. However, their relatively high cost has prevented them from fully replacing the plaster cast. In general the least satisfactory of the three techniques has been the use of the evacuated bag.